"Richard Fry" wrote in message
...
NEC in its various forms is an excellent means to evaluate the
radiation from various structures.

But without due care it still can lead to incorrect conclusions about
system performance when propagation effects are present -- as in the
recent thread here about the elevation patterns of MW monopoles.

Here is another situation...

http://i62.photobucket.com/albums/h8...PatCompare.jpg

RF

The example above does not compute the surface wave.
The following card computes "Space Wave plus SurfaceWave":

CM 144 MHz Vertical Dipole
CE
GW 1 13 0 0 33.15 0 0 30 0.010417
GS 0 0 0.304800
GE 1 -1 0
GN 2 0 0 0 13.0000 0.0050
FR 0 1 0 0 147.3 0.1
EX 0 1 7 0 65.66981572 0
LD 5 0 0 0 3.801E7
RP 1 11 1 0000 0 90 1.00000 1.00000 50000
EN

In this example the vertical half wave dipole, with the base 30 ft above
an average ground, on 147.3 MHz, shows a field strength at ground
level of: 0.418 uV/m from 30 W into the antenna.

Frank